ENC (S57) update files

I am new to using Electronic Navigation Charts (S-57). My understanding is the the ".000" files are the base datasets and subsequent updates use sequential extensions (e.g., .001, .002, .003, etc.) GM loads the .000 files without any problem -

How do you load the ENC update files? When I attempt to open .001, .002, etc., I select S-57 as the file type and receive the following error:
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Error loading S57 data.
Can't apply updates to a base file with a different extension than .000.